I searched on forge there are two-three components but I am not getting how to publish my app in AWS (Server) using those components. Can you please provide some steps to host application on AWS (Server)?

You applications are always published on the OutSystems Front-End server(s).
If you have installed the OutSystems Platform on AWS, then the OutSystems Front-End server is also on AWS and your applications are published there.

If you are using the OutSystems PaaS, in any edition (including Personal), then your applications are already published on a server running on AWS.

My purpose is that I want to make an OutSystems app platform free like Java(We can deploy war file irrespective of Java platform) I should be able to deploy it anywhere. If client has to install OutSystems on amazon also then there's no use of buying amazon servers.

To install an OutSystems application without an OutSystems Platform, you need to execute a 'detach' operation.
The 'detach' operation is available to OutSystems Enterprise customers once they decide not to renew their paid subscription.
If you are in the process of deciding for a paid subscription to the OutSystems Platform, and need to validate the operation of the detach process, please contact the OutSystems sales team, who will guide you through the alternatives.
For an overview of the detach process, check https://success.outsystems.com/Evaluation/Architecture/5_Standard_architecture_with_no_lock-in/The_process_for_detaching_apps
Once you complete the detach process, you can run the resulting application, on a supported stack (database/application server/operating system) on a server running on AWS.